Bacteriorhodopsin-based volumetric optical memory

We explore the use of the protein bacteriorhodopsin as the recording medium in an all-optical three-dimensional memory. Three-dimensional memory architectures offer as much as a thousand-fold improvement in memory storage over current storage technology. Although bacteriorhodopsin has been used previously as the active memory element in a number of three-dimensional architectures (e.g. holographic and two-photon), a sequential single-photon volumetric architecture employing a photochemical branching reaction characteristic of the protein is currently showing the most promise. This unique branching reaction allows for long-term storage by the protein. During the past two years, a prototype has been constructed by using a number of commercially available components, including spatial light modulators and microdiode lasers. Chemical, genetic, and optical technologies optimize the writing and reading efficiencies of the protein based memory. For example, gray-scale and polarization multiplexing are capable of increasing the storage capacity ten-fold. Although a number of issues still must be resolved with respect to commercialization, cost, and performance, the promise of both increased speed (via parallel reading and writing operations) and storage density, make volumetric memories a potentially viable alternative to conventional technologies.